The invention relates generally to the field of tunneling displacement sensors and more specifically to an integrated sensor module including an electron tunneling infrared sensor, such as a Golay cell.
A tunneling displacement sensor made using standard silicon wafer processing techniques and based upon a thermal detection principle, one example of a Golay cell, is described in A miniature high-sensitivity broad-band accelerometer based on electron tunneling transducers, Rockstad, Howard K., et al. Sensors and Actuators, vol. 43, pp. 107-114, 1994 and incorporated here by reference. Referring to FIG. 3, the sensor comprises a gas chamber 19, a membrane 14 at the base of the gas chamber which carries a membrane conductor 15, and a tip 23 below the membrane conductor 15 in a second chamber 17. With a proper spacing set up between the tip 23 and the membrane conductor 15, for example 10 Angstroms, tunneling action occurs. Infrared radiation impacting the sensor heats the gas in the first chamber 19 increasing the pressure on and causing displacement of the membrane 14 and conductor 15. The membrane displacement is registered as a change in the tunneling current from the tip terminal 12.
A variable high voltage bias is applied to a deflection electrode 16 creating an electrostatic force to adjust the spacing between the tip 23 and the membrane 15 for tunneling. Traditionally, the high voltage source has been manually adjusted to establish the tunneling condition which is essential for detecting any force acting on the sensor membrane.